A method well known in the art for producing polyglutamic acid consists in organic synthesis. From the industrial viewpoint, however, this method cannot be said to be an advantageous method, since it comprises polymerizing glutamic acid through a number of complicated reactions.
On the other hand, a number of reports have been presented on the fermentative production of polyglutamic acid using microorganisms since the publication of Bovarnick's work in 1942. Thus, for example, a method of producing polyglutamic acid is known which comprises cultivating a bacterial strain of the genus Bacillus, as described in Journal of Bacteriology, 76, 499 (1958), Journal of the Agricultural Chemical Society of Japan, 37, 474 (1963), or Kobunshi (High Polymers, Japan), 16, 1204 (1967).
As mentioned above, it is known that certain microorganisms can produce polyglutamic acid, and it is believed that, from the industrial viewpoint, the fermentative production of polyglutamic acid is more advantageous as compared with the chemical synthesis. It is still desired, however, that the yield should be further increased so that this substance can be supplied at reduced prices for wider application thereof in various fields.